It is 20 years since an international symposium met over a weekend to hammer out a vision for the future of Birmingham city centre. Terry Grimley looks back.

If my memory serves, the weekend of March 25-27, 1988, was grey and wet, beginning rather like the gloomy Saturday we have just endured.

It was the historic weekend when around 80 people with some kind of professional interest in Birmingham's city centre assembled for an event which was arguably one of the most important watersheds in the city's history.

Originally called the Birmingham City Centre Challenge Symposium, it has come to be known as the Highbury Initiative thanks to its neatly symbolic venue, the then recentlyrestored former home of Joseph Chamberlain, the city's most famously progressive politician.

The participants, of whom I am proud to have been one - I booked my place with a series of provocative articles about the state of Birmingham's architecture - were a mix of architects, planners, politicians, cultural leaders and other professionals from Birmingham, elsewhere in Britain and abroad.

As well as Europeans, there were several Americans and a couple of Japanese.

Notable names included leading architects Will Alsop and Terry Farrell, David Gosling, urban design adviser to London Docklands, Ed Helfeld, director of the San Francisco Redevelopment Commission, and consultant Don Hilderbrandt, from Maryland, who had already carried out a study on potential pedestrianisation in Birmingham.

Many visitors had never set foot in Birmingham before, and on Friday afternoon a series of walkabouts was organised to provide orientation.

I was in a party dropped on Fazeley Street to walk back into the centre, and I have a memory of watching Riek Bakker, Rotterdam's director of town planning and now a legendary figure for leading the transformation of another of Europe's anonymous postwar cities, lifting herself up to peer over the parapet at Birmingham's buried river, the Rea.

As we approached the city centre, then divided off from Digbeth by the elevated inner ring road at Masshouse Circus, the view amazed Ms Bakker's compatriot, the architect and planner Teun Koolhaas: "It's the most chaotic city I've ever seen," he told me. "It's as though a child had upset a box of building bricks. Haven't they heard of height-zoning?"

In other words, it took little more than a glance for visitors to see for themselves what the city council had come to realise: Birmingham was a city in trouble.

The mess left by wrong-headed, traffic-dominated postwar redevelopment might be merely a private tragedy as long as the rest of the world was interested only in the products the city made. But in a post-industrial world where a new economy depended on attracting visitors - work was already under way on the International Convention Centre - it threatened economic disaster.

So the council decided it was worth taking a punt on this American-style brainstorming symposium at a cost of £70,000, half of which was met by the Government's City Action initiative. It commissioned consultants DEGW and URBED to organise the event, which used the metaphor of theatre to structure debate.

By Sunday lunchtime a series of seminars and plenary sessions had led to a blueprint for a way forward for the city. Its main focus was on the need to downgrade the inner ring road, with through traffic diverted on to the middle ring road, still not completed at that time.

The inner ring road was seen as a physical and psychological barrier which strangled the city centre - the perception which came to be summed up in the description "concrete collar". With the removal of 1960s engineering to provide pedestrian-friendly crossings, it would be possible to expand the city centre to incorporate a ring of distinctive quarters bounded by the two ring roads - the Jewellery Quarter, the Convention Quarter, the Chinese Quarter, and so on.

Along with this should go the removal of pedestrian subways. At the final session the late Peter Rice, one of Britain's great civil engineers, described how threatened he had felt the night before walking under the underpass which then led beneath Smallbrook Queensway to Hurst Street: "Visitors need only to have one experience like that to decide never to come back to Birmingham again," he warned. "Getting rid of the underpasses is not desirable - it's essential."

And that is the advice which the city has been following ever since. In fact, so effective has the legacy of Highbury been that it now takes a considerable effort to picture the Birmingham of 1988, when the ICC, Symphony Hall and Centenary Square were still three years away, New Street was still clogged with buses, and Victoria Square existed in name but was actually a traffic roundabout.

Plans for a redevelopment of the concrete eyesore which was the 1960s Bull Ring had only just begun their long gestation period, and even Corporation Street, inside the concrete collar, was disfigured by pedestrian underpasses at the junction with Bull Street.

Whatever you think of Birmingham city centre today, it has improved vastly since those days. Much of the Highbury vision has come to be realised, and the new Big City Plan, now in development, continues seamlessly in the direction it indicated.

With the ring road now tamed and public enemy Nº 2, New Street Station, also being addressed, it can focus on opportunities such as the redevelopment of the wholesale markets and the creation of a new family-friendly residential district in Highgate connecting the city centre to the suburbs.

But there should never be any room for complacency. It's still possible, within a minute or two of leaving the bright lights of a concert at Symphony Hall or the superbly-restored Town Hall, to find yourself in a dark and threatening environment which is part of the surviving legacy of 1960s redevelopment.

* Is the vision now reality?

Birmingham City University is holding a conference, Visioning the City: 20 Years on From Highbury on Monday, April 14.

It will evaluate the impact of the initiative over the past two decades and explore its relationship to the city centre plan which is now in development.

Speakers include Sir Albert Bore, who was the city council's chair of economic devlopement at the time of Highbury, and the city's current head of development, Clive Dutton, as well as Frank Duffy of DEGW, who was one of the organisers. Lawrence Revill, of urban designers David Lock Associates, will give an outsider's assessment of Birmingham's progress over the last 20 years.

The conference organiser, architect and urban designer Joe Holyoak, said: "Essentially the structure is to devote the morning to the Highbury Initiative and then look forward to the next step, which is the Big Plan, obviously.

"We will be looking at what came out of Highbury which has been implemented and what has not. And of what has been implemented, what has worked and what hasn't.

"We'll do a little walkabout and then in the afternoon we have contributions from other cities. Sheffield, Manchester and Belfast have made big changes in the same time period, and we're inviting them to compare."

* Visioning the City takes place at Austin Court, Cambridge Street on Monday, April 14, from 9.30am-5pm. The fee is £40, including lunch. Further information from Carol Martin, Birmingham School of Architecture, BIAD, Birmingham City University, Gosta Green (0121 331 7938/carol.martin@bcu.ac.uk).